1. Field of the Invention
The present invention relates to an amplifier circuit which stabilizes an input signal and outputs a stabilized output signal.
2. Description of the Related Art
Conventionally, flat panel display devices such as liquid crystal display devices are commercialized. In particular, a small size, light weight display device is necessary for a portable device, and, for example, a liquid crystal display device is primarily used in a portable phone or the like.
In the liquid crystal display device, because high resolution images are also displayed, an active matrix type liquid crystal display device is used which has a pixel circuit in each display pixel and which can display a high-resolution image.
In the liquid crystal display device or the like, a data line is provided corresponding to each column of pixels arranged in a matrix and a data signal for each pixel is supplied to each pixel through the data line. The data line is relatively long and has a capacitor for storing a data signal. Therefore, when a data signal is supplied onto the data line, a buffer amplifier is provided to increase a current supplying capability and the signal is stabilized in advance. Such an amplifier circuit is disclosed in, for example, Japanese Patent Laid-Open Publication No. Hei 11-150427.
A difference occurs among inputs and outputs of buffer amplifiers due to, for example, variation or the like in the characteristics of the transistor which is a part of the buffer amplifier. When the voltage varies in the data for display, the display brightness varies, and thus there is a demand to minimize the variation in the voltage.